//  
//  GCDAsyncSocket.h
//  
//  This class is in the public domain.
//  Originally created by Robbie Hanson in Q3 2010.
//  Updated and maintained by Deusty LLC and the Apple development community.
//  
//  https://github.com/robbiehanson/CocoaAsyncSocket
//

#import <Foundation/Foundation.h>
#import <Security/Security.h>
#import <Security/SecureTransport.h>
#import <dispatch/dispatch.h>
#import <Availability.h>

#include <sys/socket.h> // AF_INET, AF_INET6

@class GCDAsyncReadPacket;
@class GCDAsyncWritePacket;
@class GCDAsyncSocketPreBuffer;

extern NSString *const GCDAsyncSocketException;
extern NSString *const GCDAsyncSocketErrorDomain;

extern NSString *const GCDAsyncSocketQueueName;
extern NSString *const GCDAsyncSocketThreadName;

extern NSString *const GCDAsyncSocketManuallyEvaluateTrust;
#if TARGET_OS_IPHONE
extern NSString *const GCDAsyncSocketUseCFStreamForTLS;
#endif
#define GCDAsyncSocketSSLPeerName     (NSString *)kCFStreamSSLPeerName
#define GCDAsyncSocketSSLCertificates (NSString *)kCFStreamSSLCertificates
#define GCDAsyncSocketSSLIsServer     (NSString *)kCFStreamSSLIsServer
extern NSString *const GCDAsyncSocketSSLPeerID;
extern NSString *const GCDAsyncSocketSSLProtocolVersionMin;
extern NSString *const GCDAsyncSocketSSLProtocolVersionMax;
extern NSString *const GCDAsyncSocketSSLSessionOptionFalseStart;
extern NSString *const GCDAsyncSocketSSLSessionOptionSendOneByteRecord;
extern NSString *const GCDAsyncSocketSSLCipherSuites;
#if !TARGET_OS_IPHONE
extern NSString *const GCDAsyncSocketSSLDiffieHellmanParameters;
#endif

#define GCDAsyncSocketLoggingContext 65535


enum GCDAsyncSocketError
{
    GCDAsyncSocketNoError = 0,           // Never used
    GCDAsyncSocketBadConfigError,        // Invalid configuration
    GCDAsyncSocketBadParamError,         // Invalid parameter was passed
    GCDAsyncSocketConnectTimeoutError,   // A connect operation timed out
    GCDAsyncSocketReadTimeoutError,      // A read operation timed out
    GCDAsyncSocketWriteTimeoutError,     // A write operation timed out
    GCDAsyncSocketReadMaxedOutError,     // Reached set maxLength without completing
    GCDAsyncSocketClosedError,           // The remote peer closed the connection
    GCDAsyncSocketOtherError,            // Description provided in userInfo
};
typedef enum GCDAsyncSocketError GCDAsyncSocketError;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

@interface GCDAsyncSocket : NSObject

/**
* GCDAsyncSocket uses the standard delegate paradigm,
* but executes all delegate callbacks on a given delegate dispatch queue.
* This allows for maximum concurrency, while at the same time providing easy thread safety.
*
* You MUST set a delegate AND delegate dispatch queue before attempting to
* use the socket, or you will get an error.
*
* The socket queue is optional.
* If you pass NULL, GCDAsyncSocket will automatically create it's own socket queue.
* If you choose to provide a socket queue, the socket queue must not be a concurrent queue.
* If you choose to provide a socket queue, and the socket queue has a configured target queue,
* then please see the discussion for the method markSocketQueueTargetQueue.
*
* The delegate queue and socket queue can optionally be the same.
**/
- (id)init;
- (id)initWithSocketQueue:(dispatch_queue_t)sq;
- (id)initWithDelegate:(id)aDelegate delegateQueue:(dispatch_queue_t)dq;
- (id)initWithDelegate:(id)aDelegate delegateQueue:(dispatch_queue_t)dq socketQueue:(dispatch_queue_t)sq;

#pragma mark Configuration

@property (atomic, weak, readwrite) id delegate;
#if OS_OBJECT_USE_OBJC
@property (atomic, strong, readwrite) dispatch_queue_t delegateQueue;
#else
@property (atomic, assign, readwrite) dispatch_queue_t delegateQueue;
#endif

- (void)getDelegate:(id *)delegatePtr delegateQueue:(dispatch_queue_t *)delegateQueuePtr;
- (void)setDelegate:(id)delegate delegateQueue:(dispatch_queue_t)delegateQueue;

/**
* If you are setting the delegate to nil within the delegate's dealloc method,
* you may need to use the synchronous versions below.
**/
- (void)synchronouslySetDelegate:(id)delegate;
- (void)synchronouslySetDelegateQueue:(dispatch_queue_t)delegateQueue;
- (void)synchronouslySetDelegate:(id)delegate delegateQueue:(dispatch_queue_t)delegateQueue;

/**
* By default, both IPv4 and IPv6 are enabled.
*
* For accepting incoming connections, this means GCDAsyncSocket automatically supports both protocols,
* and can simulataneously accept incoming connections on either protocol.
*
* For outgoing connections, this means GCDAsyncSocket can connect to remote hosts running either protocol.
* If a DNS lookup returns only IPv4 results, GCDAsyncSocket will automatically use IPv4.
* If a DNS lookup returns only IPv6 results, GCDAsyncSocket will automatically use IPv6.
* If a DNS lookup returns both IPv4 and IPv6 results, the preferred protocol will be chosen.
* By default, the preferred protocol is IPv4, but may be configured as desired.
**/

@property (atomic, assign, readwrite, getter=isIPv4Enabled) BOOL IPv4Enabled;
@property (atomic, assign, readwrite, getter=isIPv6Enabled) BOOL IPv6Enabled;

@property (atomic, assign, readwrite, getter=isIPv4PreferredOverIPv6) BOOL IPv4PreferredOverIPv6;

/**
* User data allows you to associate arbitrary information with the socket.
* This data is not used internally by socket in any way.
**/
@property (atomic, strong, readwrite) id userData;

#pragma mark Accepting

/**
* Tells the socket to begin listening and accepting connections on the given port.
* When a connection is accepted, a new instance of GCDAsyncSocket will be spawned to handle it,
* and the socket:didAcceptNewSocket: delegate method will be invoked.
*
* The socket will listen on all available interfaces (e.g. wifi, ethernet, etc)
**/
- (BOOL)acceptOnPort:(uint16_t)port error:(NSError **)errPtr;

/**
* This method is the same as acceptOnPort:error: with the
* additional option of specifying which interface to listen on.
*
* For example, you could specify that the socket should only accept connections over ethernet,
* and not other interfaces such as wifi.
*
* The interface may be specified by name (e.g. "en1" or "lo0") or by IP address (e.g. "192.168.4.34").
* You may also use the special strings "localhost" or "loopback" to specify that
* the socket only accept connections from the local machine.
*
* You can see the list of interfaces via the command line utility "ifconfig",
* or programmatically via the getifaddrs() function.
*
* To accept connections on any interface pass nil, or simply use the acceptOnPort:error: method.
**/
- (BOOL)acceptOnInterface:(NSString *)interface port:(uint16_t)port error:(NSError **)errPtr;

#pragma mark Connecting

/**
* Connects to the given host and port.
*
* This method invokes connectToHost:onPort:viaInterface:withTimeout:error:
* and uses the default interface, and no timeout.
**/
- (BOOL)connectToHost:(NSString *)host onPort:(uint16_t)port error:(NSError **)errPtr;

/**
* Connects to the given host and port with an optional timeout.
*
* This method invokes connectToHost:onPort:viaInterface:withTimeout:error: and uses the default interface.
**/
- (BOOL)connectToHost:(NSString *)host
               onPort:(uint16_t)port
          withTimeout:(NSTimeInterval)timeout
                error:(NSError **)errPtr;

/**
* Connects to the given host & port, via the optional interface, with an optional timeout.
*
* The host may be a domain name (e.g. "deusty.com") or an IP address string (e.g. "192.168.0.2").
* The host may also be the special strings "localhost" or "loopback" to specify connecting
* to a service on the local machine.
*
* The interface may be a name (e.g. "en1" or "lo0") or the corresponding IP address (e.g. "192.168.4.35").
* The interface may also be used to specify the local port (see below).
*
* To not time out use a negative time interval.
*
* This method will return NO if an error is detected, and set the error pointer (if one was given).
* Possible errors would be a nil host, invalid interface, or socket is already connected.
*
* If no errors are detected, this method will start a background connect operation and immediately return YES.
* The delegate callbacks are used to notify you when the socket connects, or if the host was unreachable.
*
* Since this class supports queued reads and writes, you can immediately start reading and/or writing.
* All read/write operations will be queued, and upon socket connection,
* the operations will be dequeued and processed in order.
*
* The interface may optionally contain a port number at the end of the string, separated by a colon.
* This allows you to specify the local port that should be used for the outgoing connection. (read paragraph to end)
* To specify both interface and local port: "en1:8082" or "192.168.4.35:2424".
* To specify only local port: ":8082".
* Please note this is an advanced feature, and is somewhat hidden on purpose.
* You should understand that 99.999% of the time you should NOT specify the local port for an outgoing connection.
* If you think you need to, there is a very good chance you have a fundamental misunderstanding somewhere.
* Local ports do NOT need to match remote ports. In fact, they almost never do.
* This feature is here for networking professionals using very advanced techniques.
**/
- (BOOL)connectToHost:(NSString *)host
               onPort:(uint16_t)port
         viaInterface:(NSString *)interface
          withTimeout:(NSTimeInterval)timeout
                error:(NSError **)errPtr;

/**
* Connects to the given address, specified as a sockaddr structure wrapped in a NSData object.
* For example, a NSData object returned from NSNetService's addresses method.
*
* If you have an existing struct sockaddr you can convert it to a NSData object like so:
* struct sockaddr sa  -> NSData *dsa = [NSData dataWithBytes:&remoteAddr length:remoteAddr.sa_len];
* struct sockaddr *sa -> NSData *dsa = [NSData dataWithBytes:remoteAddr length:remoteAddr->sa_len];
*
* This method invokes connectToAdd
**/
- (BOOL)connectToAddress:(NSData *)remoteAddr error:(NSError **)errPtr;

/**
* This method is the same as connectToAddress:error: with an additional timeout option.
* To not time out use a negative time interval, or simply use the connectToAddress:error: method.
**/
- (BOOL)connectToAddress:(NSData *)remoteAddr withTimeout:(NSTimeInterval)timeout error:(NSError **)errPtr;

/**
* Connects to the given address, using the specified interface and timeout.
*
* The address is specified as a sockaddr structure wrapped in a NSData object.
* For example, a NSData object returned from NSNetService's addresses method.
*
* If you have an existing struct sockaddr you can convert it to a NSData object like so:
* struct sockaddr sa  -> NSData *dsa = [NSData dataWithBytes:&remoteAddr length:remoteAddr.sa_len];
* struct sockaddr *sa -> NSData *dsa = [NSData dataWithBytes:remoteAddr length:remoteAddr->sa_len];
*
* The interface may be a name (e.g. "en1" or "lo0") or the corresponding IP address (e.g. "192.168.4.35").
* The interface may also be used to specify the local port (see below).
*
* The timeout is optional. To not time out use a negative time interval.
*
* This method will return NO if an error is detected, and set the error pointer (if one was given).
* Possible errors would be a nil host, invalid interface, or socket is already connected.
*
* If no errors are detected, this method will start a background connect operation and immediately return YES.
* The delegate callbacks are used to notify you when the socket connects, or if the host was unreachable.
*
* Since this class supports queued reads and writes, you can immediately start reading and/or writing.
* All read/write operations will be queued, and upon socket connection,
* the operations will be dequeued and processed in order.
*
* The interface may optionally contain a port number at the end of the string, separated by a colon.
* This allows you to specify the local port that should be used for the outgoing connection. (read paragraph to end)
* To specify both interface and local port: "en1:8082" or "192.168.4.35:2424".
* To specify only local port: ":8082".
* Please note this is an advanced feature, and is somewhat hidden on purpose.
* You should understand that 99.999% of the time you should NOT specify the local port for an outgoing connection.
* If you think you need to, there is a very good chance you have a fundamental misunderstanding somewhere.
* Local ports do NOT need to match remote ports. In fact, they almost never do.
* This feature is here for networking professionals using very advanced techniques.
**/
- (BOOL)connectToAddress:(NSData *)remoteAddr
            viaInterface:(NSString *)interface
             withTimeout:(NSTimeInterval)timeout
                   error:(NSError **)errPtr;

#pragma mark Disconnecting

/**
* Disconnects immediately (synchronously). Any pending reads or writes are dropped.
*
* If the socket is not already disconnected, an invocation to the socketDidDisconnect:withError: delegate method
* will be queued onto the delegateQueue asynchronously (behind any previously queued delegate methods).
* In other words, the disconnected delegate method will be invoked sometime shortly after this method returns.
*
* Please note the recommended way of releasing a GCDAsyncSocket instance (e.g. in a dealloc method)
* [asyncSocket setDelegate:nil];
* [asyncSocket disconnect];
* [asyncSocket release];
*
* If you plan on disconnecting the socket, and then immediately asking it to connect again,
* you'll likely want to do so like this:
* [asyncSocket setDelegate:nil];
* [asyncSocket disconnect];
* [asyncSocket setDelegate:self];
* [asyncSocket connect...];
**/
- (void)disconnect;

/**
* Disconnects after all pending reads have completed.
* After calling this, the read and write methods will do nothing.
* The socket will disconnect even if there are still pending writes.
**/
- (void)disconnectAfterReading;

/**
* Disconnects after all pending writes have completed.
* After calling this, the read and write methods will do nothing.
* The socket will disconnect even if there are still pending reads.
**/
- (void)disconnectAfterWriting;

/**
* Disconnects after all pending reads and writes have completed.
* After calling this, the read and write methods will do nothing.
**/
- (void)disconnectAfterReadingAndWriting;

#pragma mark Diagnostics

- (NSError *)connectTimeoutError;

- (NSError *)writeTimeoutError;

/**
* Returns whether the socket is disconnected or connected.
*
* A disconnected socket may be recycled.
* That is, it can used again for connecting or listening.
*
* If a socket is in the process of connecting, it may be neither disconnected nor connected.
**/
@property (atomic, readonly) BOOL isDisconnected;
@property (atomic, readonly) BOOL isConnected;

/**
* Returns the local or remote host and port to which this socket is connected, or nil and 0 if not connected.
* The host will be an IP address.
**/
@property (atomic, readonly) NSString *connectedHost;
@property (atomic, readonly) uint16_t  connectedPort;

@property (atomic, readonly) NSString *localHost;
@property (atomic, readonly) uint16_t  localPort;

/**
* Returns the local or remote address to which this socket is connected,
* specified as a sockaddr structure wrapped in a NSData object.
*
* @seealso connectedHost
* @seealso connectedPort
* @seealso localHost
* @seealso localPort
**/
@property (atomic, readonly) NSData *connectedAddress;
@property (atomic, readonly) NSData *localAddress;

/**
* Returns whether the socket is IPv4 or IPv6.
* An accepting socket may be both.
**/
@property (atomic, readonly) BOOL isIPv4;
@property (atomic, readonly) BOOL isIPv6;

/**
* Returns whether or not the socket has been secured via SSL/TLS.
*
* See also the startTLS method.
**/
@property (atomic, readonly) BOOL isSecure;

#pragma mark Reading

// The readData and writeData methods won't block (they are asynchronous).
// 
// When a read is complete the socket:didReadData:withTag: delegate method is dispatched on the delegateQueue.
// When a write is complete the socket:didWriteDataWithTag: delegate method is dispatched on the delegateQueue.
// 
// You may optionally set a timeout for any read/write operation. (To not timeout, use a negative time interval.)
// If a read/write opertion times out, the corresponding "socket:shouldTimeout..." delegate method
// is called to optionally allow you to extend the timeout.
// Upon a timeout, the "socket:didDisconnectWithError:" method is called
// 
// The tag is for your convenience.
// You can use it as an array index, step number, state id, pointer, etc.

/**
* Reads the first available bytes that become available on the socket.
*
* If the timeout value is negative, the read operation will not use a timeout.
**/
- (void)readDataWithTimeout:(NSTimeInterval)timeout tag:(long)tag;

/**
* Reads the first available bytes that become available on the socket.
* The bytes will be appended to the given byte buffer starting at the given offset.
* The given buffer will automatically be increased in size if needed.
*
* If the timeout value is negative, the read operation will not use a timeout.
* If the buffer if nil, the socket will create a buffer for you.
*
* If the bufferOffset is greater than the length of the given buffer,
* the method will do nothing, and the delegate will not be called.
*
* If you pass a buffer, you must not alter it in any way while the socket is using it.
* After completion, the data returned in socket:didReadData:withTag: will be a subset of the given buffer.
* That is, it will reference the bytes that were appended to the given buffer via
* the method [NSData dataWithBytesNoCopy:length:freeWhenDone:NO].
**/
- (void)readDataWithTimeout:(NSTimeInterval)timeout
                     buffer:(NSMutableData *)buffer
               bufferOffset:(NSUInteger)offset
                        tag:(long)tag;

/**
* Reads the first available bytes that become available on the socket.
* The bytes will be appended to the given byte buffer starting at the given offset.
* The given buffer will automatically be increased in size if needed.
* A maximum of length bytes will be read.
*
* If the timeout value is negative, the read operation will not use a timeout.
* If the buffer if nil, a buffer will automatically be created for you.
* If maxLength is zero, no length restriction is enforced.
*
* If the bufferOffset is greater than the length of the given buffer,
* the method will do nothing, and the delegate will not be called.
*
* If you pass a buffer, you must not alter it in any way while the socket is using it.
* After completion, the data returned in socket:didReadData:withTag: will be a subset of the given buffer.
* That is, it will reference the bytes that were appended to the given buffer  via
* the method [NSData dataWithBytesNoCopy:length:freeWhenDone:NO].
**/
- (void)readDataWithTimeout:(NSTimeInterval)timeout
                     buffer:(NSMutableData *)buffer
               bufferOffset:(NSUInteger)offset
                  maxLength:(NSUInteger)length
                        tag:(long)tag;

/**
* Reads the given number of bytes.
*
* If the timeout value is negative, the read operation will not use a timeout.
*
* If the length is 0, this method does nothing and the delegate is not called.
**/
- (void)readDataToLength:(NSUInteger)length withTimeout:(NSTimeInterval)timeout tag:(long)tag;

/**
* Reads the given number of bytes.
* The bytes will be appended to the given byte buffer starting at the given offset.
* The given buffer will automatically be increased in size if needed.
*
* If the timeout value is negative, the read operation will not use a timeout.
* If the buffer if nil, a buffer will automatically be created for you.
*
* If the length is 0, this method does nothing and the delegate is not called.
* If the bufferOffset is greater than the length of the given buffer,
* the method will do nothing, and the delegate will not be called.
*
* If you pass a buffer, you must not alter it in any way while AsyncSocket is using it.
* After completion, the data returned in socket:didReadData:withTag: will be a subset of the given buffer.
* That is, it will reference the bytes that were appended to the given buffer via
* the method [NSData dataWithBytesNoCopy:length:freeWhenDone:NO].
**/
- (void)readDataToLength:(NSUInteger)length
             withTimeout:(NSTimeInterval)timeout
                  buffer:(NSMutableData *)buffer
            bufferOffset:(NSUInteger)offset
                     tag:(long)tag;

/**
* Reads bytes until (and including) the passed "data" parameter, which acts as a separator.
*
* If the timeout value is negative, the read operation will not use a timeout.
*
* If you pass nil or zero-length data as the "data" parameter,
* the method will do nothing (except maybe print a warning), and the delegate will not be called.
*
* To read a line from the socket, use the line separator (e.g. CRLF for HTTP, see below) as the "data" parameter.
* If you're developing your own custom protocol, be sure your separator can not occur naturally as
* part of the data between separators.
* For example, imagine you want to send several small documents over a socket.
* Using CRLF as a separator is likely unwise, as a CRLF could easily exist within the documents.
* In this particular example, it would be better to use a protocol similar to HTTP with
* a header that includes the length of the document.
* Also be careful that your separator cannot occur naturally as part of the encoding for a character.
*
* The given data (separator) parameter should be immutable.
* For performance reasons, the socket will retain it, not copy it.
* So if it is immutable, don't modify it while the socket is using it.
**/
- (void)readDataToData:(NSData *)data withTimeout:(NSTimeInterval)timeout tag:(long)tag;

/**
* Reads bytes until (and including) the passed "data" parameter, which acts as a separator.
* The bytes will be appended to the given byte buffer starting at the given offset.
* The given buffer will automatically be increased in size if needed.
*
* If the timeout value is negative, the read operation will not use a timeout.
* If the buffer if nil, a buffer will automatically be created for you.
*
* If the bufferOffset is greater than the length of the given buffer,
* the method will do nothing (except maybe print a warning), and the delegate will not be called.
*
* If you pass a buffer, you must not alter it in any way while the socket is using it.
* After completion, the data returned in socket:didReadData:withTag: will be a subset of the given buffer.
* That is, it will reference the bytes that were appended to the given buffer via
* the method [NSData dataWithBytesNoCopy:length:freeWhenDone:NO].
*
* To read a line from the socket, use the line separator (e.g. CRLF for HTTP, see below) as the "data" parameter.
* If you're developing your own custom protocol, be sure your separator can not occur naturally as
* part of the data between separators.
* For example, imagine you want to send several small documents over a socket.
* Using CRLF as a separator is likely unwise, as a CRLF could easily exist within the documents.
* In this particular example, it would be better to use a protocol similar to HTTP with
* a header that includes the length of the document.
* Also be careful that your separator cannot occur naturally as part of the encoding for a character.
*
* The given data (separator) parameter should be immutable.
* For performance reasons, the socket will retain it, not copy it.
* So if it is immutable, don't modify it while the socket is using it.
**/
- (void)readDataToData:(NSData *)data
           withTimeout:(NSTimeInterval)timeout
                buffer:(NSMutableData *)buffer
          bufferOffset:(NSUInteger)offset
                   tag:(long)tag;

/**
* Reads bytes until (and including) the passed "data" parameter, which acts as a separator.
*
* If the timeout value is negative, the read operation will not use a timeout.
*
* If maxLength is zero, no length restriction is enforced.
* Otherwise if maxLength bytes are read without completing the read,
* it is treated similarly to a timeout - the socket is closed with a GCDAsyncSocketReadMaxedOutError.
* The read will complete successfully if exactly maxLength bytes are read and the given data is found at the end.
*
* If you pass nil or zero-length data as the "data" parameter,
* the method will do nothing (except maybe print a warning), and the delegate will not be called.
* If you pass a maxLength parameter that is less than the length of the data parameter,
* the method will do nothing (except maybe print a warning), and the delegate will not be called.
*
* To read a line from the socket, use the line separator (e.g. CRLF for HTTP, see below) as the "data" parameter.
* If you're developing your own custom protocol, be sure your separator can not occur naturally as
* part of the data between separators.
* For example, imagine you want to send several small documents over a socket.
* Using CRLF as a separator is likely unwise, as a CRLF could easily exist within the documents.
* In this particular example, it would be better to use a protocol similar to HTTP with
* a header that includes the length of the document.
* Also be careful that your separator cannot occur naturally as part of the encoding for a character.
*
* The given data (separator) parameter should be immutable.
* For performance reasons, the socket will retain it, not copy it.
* So if it is immutable, don't modify it while the socket is using it.
**/
- (void)readDataToData:(NSData *)data withTimeout:(NSTimeInterval)timeout maxLength:(NSUInteger)length tag:(long)tag;

/**
* Reads bytes until (and including) the passed "data" parameter, which acts as a separator.
* The bytes will be appended to the given byte buffer starting at the given offset.
* The given buffer will automatically be increased in size if needed.
*
* If the timeout value is negative, the read operation will not use a timeout.
* If the buffer if nil, a buffer will automatically be created for you.
*
* If maxLength is zero, no length restriction is enforced.
* Otherwise if maxLength bytes are read without completing the read,
* it is treated similarly to a timeout - the socket is closed with a GCDAsyncSocketReadMaxedOutError.
* The read will complete successfully if exactly maxLength bytes are read and the given data is found at the end.
*
* If you pass a maxLength parameter that is less than the length of the data (separator) parameter,
* the method will do nothing (except maybe print a warning), and the delegate will not be called.
* If the bufferOffset is greater than the length of the given buffer,
* the method will do nothing (except maybe print a warning), and the delegate will not be called.
*
* If you pass a buffer, you must not alter it in any way while the socket is using it.
* After completion, the data returned in socket:didReadData:withTag: will be a subset of the given buffer.
* That is, it will reference the bytes that were appended to the given buffer via
* the method [NSData dataWithBytesNoCopy:length:freeWhenDone:NO].
*
* To read a line from the socket, use the line separator (e.g. CRLF for HTTP, see below) as the "data" parameter.
* If you're developing your own custom protocol, be sure your separator can not occur naturally as
* part of the data between separators.
* For example, imagine you want to send several small documents over a socket.
* Using CRLF as a separator is likely unwise, as a CRLF could easily exist within the documents.
* In this particular example, it would be better to use a protocol similar to HTTP with
* a header that includes the length of the document.
* Also be careful that your separator cannot occur naturally as part of the encoding for a character.
*
* The given data (separator) parameter should be immutable.
* For performance reasons, the socket will retain it, not copy it.
* So if it is immutable, don't modify it while the socket is using it.
**/
- (void)readDataToData:(NSData *)data
           withTimeout:(NSTimeInterval)timeout
                buffer:(NSMutableData *)buffer
          bufferOffset:(NSUInteger)offset
             maxLength:(NSUInteger)length
                   tag:(long)tag;

/**
* Returns progress of the current read, from 0.0 to 1.0, or NaN if no current read (use isnan() to check).
* The parameters "tag", "done" and "total" will be filled in if they aren't NULL.
**/
- (float)progressOfReadReturningTag:(long *)tagPtr bytesDone:(NSUInteger *)donePtr total:(NSUInteger *)totalPtr;

#pragma mark Writing

/**
* Writes data to the socket, and calls the delegate when finished.
*
* If you pass in nil or zero-length data, this method does nothing and the delegate will not be called.
* If the timeout value is negative, the write operation will not use a timeout.
*
* Thread-Safety Note:
* If the given data parameter is mutable (NSMutableData) then you MUST NOT alter the data while
* the socket is writing it. In other words, it's not safe to alter the data until after the delegate method
* socket:didWriteDataWithTag: is invoked signifying that this particular write operation has completed.
* This is due to the fact that GCDAsyncSocket does NOT copy the data. It simply retains it.
* This is for performance reasons. Often times, if NSMutableData is passed, it is because
* a request/response was built up in memory. Copying this data adds an unwanted/unneeded overhead.
* If you need to write data from an immutable buffer, and you need to alter the buffer before the socket
* completes writing the bytes (which is NOT immediately after this method returns, but rather at a later time
* when the delegate method notifies you), then you should first copy the bytes, and pass the copy to this method.
**/
- (void)writeData:(NSData *)data withTimeout:(NSTimeInterval)timeout tag:(long)tag;

/**
* Returns progress of the current write, from 0.0 to 1.0, or NaN if no current write (use isnan() to check).
* The parameters "tag", "done" and "total" will be filled in if they aren't NULL.
**/
- (float)progressOfWriteReturningTag:(long *)tagPtr bytesDone:(NSUInteger *)donePtr total:(NSUInteger *)totalPtr;

#pragma mark Security

/**
* Secures the connection using SSL/TLS.
*
* This method may be called at any time, and the TLS handshake will occur after all pending reads and writes
* are finished. This allows one the option of sending a protocol dependent StartTLS message, and queuing
* the upgrade to TLS at the same time, without having to wait for the write to finish.
* Any reads or writes scheduled after this method is called will occur over the secured connection.
*
* ==== The available TOP-LEVEL KEYS are:
*
* - GCDAsyncSocketManuallyEvaluateTrust
*     The value must be of type NSNumber, encapsulating a BOOL value.
*     If you set this to YES, then the underlying SecureTransport system will not evaluate the SecTrustRef of the peer.
*     Instead it will pause at the moment evaulation would typically occur,
*     and allow us to handle the security evaluation however we see fit.
*     So GCDAsyncSocket will invoke the delegate method socket:shouldTrustPeer: passing the SecTrustRef.
*
*     Note that if you set this option, then all other configuration keys are ignored.
*     Evaluation will be completely up to you during the socket:didReceiveTrust:completionHandler: delegate method.
*
*     For more information on trust evaluation see:
*     Apple's Technical Note TN2232 - HTTPS Server Trust Evaluation
*     https://developer.apple.com/library/ios/technotes/tn2232/_index.html
*
*     If unspecified, the default value is NO.
*
* - GCDAsyncSocketUseCFStreamForTLS (iOS only)
*     The value must be of type NSNumber, encapsulating a BOOL value.
*     By default GCDAsyncSocket will use the SecureTransport layer to perform encryption.
*     This gives us more control over the security protocol (many more configuration options),
*     plus it allows us to optimize things like sys calls and buffer allocation.
*
*     However, if you absolutely must, you can instruct GCDAsyncSocket to use the old-fashioned encryption
*     technique by going through the CFStream instead. So instead of using SecureTransport, GCDAsyncSocket
*     will instead setup a CFRead/CFWriteStream. And then set the kCFStreamPropertySSLSettings property
*     (via CFReadStreamSetProperty / CFWriteStreamSetProperty) and will pass the given options to this method.
*
*     Thus all the other keys in the given dictionary will be ignored by GCDAsyncSocket,
*     and will passed directly CFReadStreamSetProperty / CFWriteStreamSetProperty.
*     For more infomation on these keys, please see the documentation for kCFStreamPropertySSLSettings.
*
*     If unspecified, the default value is NO.
*
* ==== The available CONFIGURATION KEYS are:
*
* - kCFStreamSSLPeerName
*     The value must be of type NSString.
*     It should match the name in the X.509 certificate given by the remote party.
*     See Apple's documentation for SSLSetPeerDomainName.
*
* - kCFStreamSSLCertificates
*     The value must be of type NSArray.
*     See Apple's documentation for SSLSetCertificate.
*
* - kCFStreamSSLIsServer
*     The value must be of type NSNumber, encapsulationg a BOOL value.
*     See Apple's documentation for SSLCreateContext for iOS.
*     This is optional for iOS. If not supplied, a NO value is the default.
*     This is not needed for Mac OS X, and the value is ignored.
*
* - GCDAsyncSocketSSLPeerID
*     The value must be of type NSData.
*     You must set this value if you want to use TLS session resumption.
*     See Apple's documentation for SSLSetPeerID.
*
* - GCDAsyncSocketSSLProtocolVersionMin
* - GCDAsyncSocketSSLProtocolVersionMax
*     The value(s) must be of type NSNumber, encapsulting a SSLProtocol value.
*     See Apple's documentation for SSLSetProtocolVersionMin & SSLSetProtocolVersionMax.
*     See also the SSLProtocol typedef.
*
* - GCDAsyncSocketSSLSessionOptionFalseStart
*     The value must be of type NSNumber, encapsulating a BOOL value.
*     See Apple's documentation for kSSLSessionOptionFalseStart.
*
* - GCDAsyncSocketSSLSessionOptionSendOneByteRecord
*     The value must be of type NSNumber, encapsulating a BOOL value.
*     See Apple's documentation for kSSLSessionOptionSendOneByteRecord.
*
* - GCDAsyncSocketSSLCipherSuites
*     The values must be of type NSArray.
*     Each item within the array must be a NSNumber, encapsulating
*     See Apple's documentation for SSLSetEnabledCiphers.
*     See also the SSLCipherSuite typedef.
*
* - GCDAsyncSocketSSLDiffieHellmanParameters (Mac OS X only)
*     The value must be of type NSData.
*     See Apple's documentation for SSLSetDiffieHellmanParams.
*
* ==== The following UNAVAILABLE KEYS are: (with throw an exception)
*
* - kCFStreamSSLAllowsAnyRoot (UNAVAILABLE)
*     You MUST use manual trust evaluation instead (see GCDAsyncSocketManuallyEvaluateTrust).
*     Corresponding deprecated method: SSLSetAllowsAnyRoot
*
* - kCFStreamSSLAllowsExpiredRoots (UNAVAILABLE)
*     You MUST use manual trust evaluation instead (see GCDAsyncSocketManuallyEvaluateTrust).
*     Corresponding deprecated method: SSLSetAllowsExpiredRoots
*
* - kCFStreamSSLAllowsExpiredCertificates (UNAVAILABLE)
*     You MUST use manual trust evaluation instead (see GCDAsyncSocketManuallyEvaluateTrust).
*     Corresponding deprecated method: SSLSetAllowsExpiredCerts
*
* - kCFStreamSSLValidatesCertificateChain (UNAVAILABLE)
*     You MUST use manual trust evaluation instead (see GCDAsyncSocketManuallyEvaluateTrust).
*     Corresponding deprecated method: SSLSetEnableCertVerify
*
* - kCFStreamSSLLevel (UNAVAILABLE)
*     You MUST use GCDAsyncSocketSSLProtocolVersionMin & GCDAsyncSocketSSLProtocolVersionMin instead.
*     Corresponding deprecated method: SSLSetProtocolVersionEnabled
*
*
* Please refer to Apple's documentation for corresponding SSLFunctions.
*
* If you pass in nil or an empty dictionary, the default settings will be used.
*
* IMPORTANT SECURITY NOTE:
* The default settings will check to make sure the remote party's certificate is signed by a
* trusted 3rd party certificate agency (e.g. verisign) and that the certificate is not expired.
* However it will not verify the name on the certificate unless you
* give it a name to verify against via the kCFStreamSSLPeerName key.
* The security implications of this are important to understand.
* Imagine you are attempting to create a secure connection to MySecureServer.com,
* but your socket gets directed to MaliciousServer.com because of a hacked DNS server.
* If you simply use the default settings, and MaliciousServer.com has a valid certificate,
* the default settings will not detect any problems since the certificate is valid.
* To properly secure your connection in this particular scenario you
* should set the kCFStreamSSLPeerName property to "MySecureServer.com".
*
* You can also perform additional validation in socketDidSecure.
**/
- (void)startTLS:(NSDictionary *)tlsSettings;

#pragma mark Advanced

/**
* Traditionally sockets are not closed until the conversation is over.
* However, it is technically possible for the remote enpoint to close its write stream.
* Our socket would then be notified that there is no more data to be read,
* but our socket would still be writeable and the remote endpoint could continue to receive our data.
*
* The argument for this confusing functionality stems from the idea that a client could shut down its
* write stream after sending a request to the server, thus notifying the server there are to be no further requests.
* In practice, however, this technique did little to help server developers.
*
* To make matters worse, from a TCP perspective there is no way to tell the difference from a read stream close
* and a full socket close. They both result in the TCP stack receiving a FIN packet. The only way to tell
* is by continuing to write to the socket. If it was only a read stream close, then writes will continue to work.
* Otherwise an error will be occur shortly (when the remote end sends us a RST packet).
*
* In addition to the technical challenges and confusion, many high level socket/stream API's provide
* no support for dealing with the problem. If the read stream is closed, the API immediately declares the
* socket to be closed, and shuts down the write stream as well. In fact, this is what Apple's CFStream API does.
* It might sound like poor design at first, but in fact it simplifies development.
*
* The vast majority of the time if the read stream is closed it's because the remote endpoint closed its socket.
* Thus it actually makes sense to close the socket at this point.
* And in fact this is what most networking developers want and expect to happen.
* However, if you are writing a server that interacts with a plethora of clients,
* you might encounter a client that uses the discouraged technique of shutting down its write stream.
* If this is the case, you can set this property to NO,
* and make use of the socketDidCloseReadStream delegate method.
*
* The default value is YES.
**/
@property (atomic, assign, readwrite) BOOL autoDisconnectOnClosedReadStream;

/**
* GCDAsyncSocket maintains thread safety by using an internal serial dispatch_queue.
* In most cases, the instance creates this queue itself.
* However, to allow for maximum flexibility, the internal queue may be passed in the init method.
* This allows for some advanced options such as controlling socket priority via target queues.
* However, when one begins to use target queues like this, they open the door to some specific deadlock issues.
*
* For example, imagine there are 2 queues:
* dispatch_queue_t socketQueue;
* dispatch_queue_t socketTargetQueue;
*
* If you do this (pseudo-code):
* socketQueue.targetQueue = socketTargetQueue;
*
* Then all socketQueue operations will actually get run on the given socketTargetQueue.
* This is fine and works great in most situations.
* But if you run code directly from within the socketTargetQueue that accesses the socket,
* you could potentially get deadlock. Imagine the following code:
*
* - (BOOL)socketHasSomething
* {
*     __block BOOL result = NO;
*     dispatch_block_t block = ^{
*         result = [self someInternalMethodToBeRunOnlyOnSocketQueue];
*     }
*     if (is_executing_on_queue(socketQueue))
*         block();
*     else
*         dispatch_sync(socketQueue, block);
*
*     return result;
* }
*
* What happens if you call this method from the socketTargetQueue? The result is deadlock.
* This is because the GCD API offers no mechanism to discover a queue's targetQueue.
* Thus we have no idea if our socketQueue is configured with a targetQueue.
* If we had this information, we could easily avoid deadlock.
* But, since these API's are missing or unfeasible, you'll have to explicitly set it.
*
* IF you pass a socketQueue via the init method,
* AND you've configured the passed socketQueue with a targetQueue,
* THEN you should pass the end queue in the target hierarchy.
*
* For example, consider the following queue hierarchy:
* socketQueue -> ipQueue -> moduleQueue
*
* This example demonstrates priority shaping within some server.
* All incoming client connections from the same IP address are executed on the same target queue.
* And all connections for a particular module are executed on the same target queue.
* Thus, the priority of all networking for the entire module can be changed on the fly.
* Additionally, networking traffic from a single IP cannot monopolize the module.
*
* Here's how you would accomplish something like that:
* - (dispatch_queue_t)newSocketQueueForConnectionFromAddress:(NSData *)address onSocket:(GCDAsyncSocket *)sock
* {
*     dispatch_queue_t socketQueue = dispatch_queue_create("", NULL);
*     dispatch_queue_t ipQueue = [self ipQueueForAddress:address];
*
*     dispatch_set_target_queue(socketQueue, ipQueue);
*     dispatch_set_target_queue(iqQueue, moduleQueue);
*
*     return socketQueue;
* }
* - (void)socket:(GCDAsyncSocket *)sock didAcceptNewSocket:(GCDAsyncSocket *)newSocket
* {
*     [clientConnections addObject:newSocket];
*     [newSocket markSocketQueueTargetQueue:moduleQueue];
* }
*
* Note: This workaround is ONLY needed if you intend to execute code directly on the ipQueue or moduleQueue.
* This is often NOT the case, as such queues are used solely for execution shaping.
**/
- (void)markSocketQueueTargetQueue:(dispatch_queue_t)socketQueuesPreConfiguredTargetQueue;
- (void)unmarkSocketQueueTargetQueue:(dispatch_queue_t)socketQueuesPreviouslyConfiguredTargetQueue;

/**
* It's not thread-safe to access certain variables from outside the socket's internal queue.
*
* For example, the socket file descriptor.
* File descriptors are simply integers which reference an index in the per-process file table.
* However, when one requests a new file descriptor (by opening a file or socket),
* the file descriptor returned is guaranteed to be the lowest numbered unused descriptor.
* So if we're not careful, the following could be possible:
*
* - Thread A invokes a method which returns the socket's file descriptor.
* - The socket is closed via the socket's internal queue on thread B.
* - Thread C opens a file, and subsequently receives the file descriptor that was previously the socket's FD.
* - Thread A is now accessing/altering the file instead of the socket.
*
* In addition to this, other variables are not actually objects,
* and thus cannot be retained/released or even autoreleased.
* An example is the sslContext, of type SSLContextRef, which is actually a malloc'd struct.
*
* Although there are internal variables that make it difficult to maintain thread-safety,
* it is important to provide access to these variables
* to ensure this class can be used in a wide array of environments.
* This method helps to accomplish this by invoking the current block on the socket's internal queue.
* The methods below can be invoked from within the block to access
* those generally thread-unsafe internal variables in a thread-safe manner.
* The given block will be invoked synchronously on the socket's internal queue.
*
* If you save references to any protected variables and use them outside the block, you do so at your own peril.
**/
- (void)performBlock:(dispatch_block_t)block;

/**
* These methods are only available from within the context of a performBlock: invocation.
* See the documentation for the performBlock: method above.
*
* Provides access to the socket's file descriptor(s).
* If the socket is a server socket (is accepting incoming connections),
* it might actually have multiple internal socket file descriptors - one for IPv4 and one for IPv6.
**/
- (int)socketFD;
- (int)socket4FD;
- (int)socket6FD;

#if TARGET_OS_IPHONE

/**
 * These methods are only available from within the context of a performBlock: invocation.
 * See the documentation for the performBlock: method above.
 * 
 * Provides access to the socket's internal CFReadStream/CFWriteStream.
 * 
 * These streams are only used as workarounds for specific iOS shortcomings:
 * 
 * - Apple has decided to keep the SecureTransport framework private is iOS.
 *   This means the only supplied way to do SSL/TLS is via CFStream or some other API layered on top of it.
 *   Thus, in order to provide SSL/TLS support on iOS we are forced to rely on CFStream,
 *   instead of the preferred and faster and more powerful SecureTransport.
 * 
 * - If a socket doesn't have backgrounding enabled, and that socket is closed while the app is backgrounded,
 *   Apple only bothers to notify us via the CFStream API.
 *   The faster and more powerful GCD API isn't notified properly in this case.
 * 
 * See also: (BOOL)enableBackgroundingOnSocket
**/
- (CFReadStreamRef)readStream;
- (CFWriteStreamRef)writeStream;

/**
 * This method is only available from within the context of a performBlock: invocation.
 * See the documentation for the performBlock: method above.
 * 
 * Configures the socket to allow it to operate when the iOS application has been backgrounded.
 * In other words, this method creates a read & write stream, and invokes:
 * 
 * CFReadStreamSetProperty(readStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
 * CFWriteStreamSetProperty(writeStream, kCFStreamNetworkServiceType, kCFStreamNetworkServiceTypeVoIP);
 * 
 * Returns YES if successful, NO otherwise.
 * 
 * Note: Apple does not officially support backgrounding server sockets.
 * That is, if your socket is accepting incoming connections, Apple does not officially support
 * allowing iOS applications to accept incoming connections while an app is backgrounded.
 * 
 * Example usage:
 * 
 * - (void)socket:(GCDAsyncSocket *)sock didConnectToHost:(NSString *)host port:(uint16_t)port
 * {
 *     [asyncSocket performBlock:^{
 *         [asyncSocket enableBackgroundingOnSocket];
 *     }];
 * }
**/
- (BOOL)enableBackgroundingOnSocket;

#endif

/**
* This method is only available from within the context of a performBlock: invocation.
* See the documentation for the performBlock: method above.
*
* Provides access to the socket's SSLContext, if SSL/TLS has been started on the socket.
**/
- (SSLContextRef)sslContext;

#pragma mark Utilities

/**
* The address lookup utility used by the class.
* This method is synchronous, so it's recommended you use it on a background thread/queue.
*
* The special strings "localhost" and "loopback" return the loopback address for IPv4 and IPv6.
*
* @returns
*   A mutable array with all IPv4 and IPv6 addresses returned by getaddrinfo.
*   The addresses are specifically for TCP connections.
*   You can filter the addresses, if needed, using the other utility methods provided by the class.
**/
+ (NSMutableArray *)lookupHost:(NSString *)host port:(uint16_t)port error:(NSError **)errPtr;

/**
* Extracting host and port information from raw address data.
**/

+ (NSString *)hostFromAddress:(NSData *)address;
+ (uint16_t)portFromAddress:(NSData *)address;

+ (BOOL)isIPv4Address:(NSData *)address;
+ (BOOL)isIPv6Address:(NSData *)address;

+ (BOOL)getHost:(NSString **)hostPtr port:(uint16_t *)portPtr fromAddress:(NSData *)address;

+ (BOOL)getHost:(NSString **)hostPtr port:(uint16_t *)portPtr family:(sa_family_t *)afPtr fromAddress:(NSData *)address;

/**
* A few common line separators, for use with the readDataToData:... methods.
**/
+ (NSData *)CRLFData;   // 0x0D0A
+ (NSData *)CRData;     // 0x0D
+ (NSData *)LFData;     // 0x0A
+ (NSData *)ZeroData;   // 0x00

@end

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark -
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

@protocol GCDAsyncSocketDelegate
@optional

/**
* This method is called immediately prior to socket:didAcceptNewSocket:.
* It optionally allows a listening socket to specify the socketQueue for a new accepted socket.
* If this method is not implemented, or returns NULL, the new accepted socket will create its own default queue.
*
* Since you cannot autorelease a dispatch_queue,
* this method uses the "new" prefix in its name to specify that the returned queue has been retained.
*
* Thus you could do something like this in the implementation:
* return dispatch_queue_create("MyQueue", NULL);
*
* If you are placing multiple sockets on the same queue,
* then care should be taken to increment the retain count each time this method is invoked.
*
* For example, your implementation might look something like this:
* dispatch_retain(myExistingQueue);
* return myExistingQueue;
**/
- (dispatch_queue_t)newSocketQueueForConnectionFromAddress:(NSData *)address onSocket:(GCDAsyncSocket *)sock;

/**
* Called when a socket accepts a connection.
* Another socket is automatically spawned to handle it.
*
* You must retain the newSocket if you wish to handle the connection.
* Otherwise the newSocket instance will be released and the spawned connection will be closed.
*
* By default the new socket will have the same delegate and delegateQueue.
* You may, of course, change this at any time.
**/
- (void)socket:(GCDAsyncSocket *)sock didAcceptNewSocket:(GCDAsyncSocket *)newSocket;

/**
* Called when a socket connects and is ready for reading and writing.
* The host parameter will be an IP address, not a DNS name.
**/
- (void)socket:(GCDAsyncSocket *)sock didConnectToHost:(NSString *)host port:(uint16_t)port;

/**
* Called when a socket has completed reading the requested data into memory.
* Not called if there is an error.
**/
- (void)socket:(GCDAsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag;

/**
* Called when a socket has read in data, but has not yet completed the read.
* This would occur if using readToData: or readToLength: methods.
* It may be used to for things such as updating progress bars.
**/
- (void)socket:(GCDAsyncSocket *)sock didReadPartialDataOfLength:(NSUInteger)partialLength tag:(long)tag;

/**
* Called when a socket has completed writing the requested data. Not called if there is an error.
**/
- (void)socket:(GCDAsyncSocket *)sock didWriteDataWithTag:(long)tag;

/**
* Called when a socket has written some data, but has not yet completed the entire write.
* It may be used to for things such as updating progress bars.
**/
- (void)socket:(GCDAsyncSocket *)sock didWritePartialDataOfLength:(NSUInteger)partialLength tag:(long)tag;

/**
* Called if a read operation has reached its timeout without completing.
* This method allows you to optionally extend the timeout.
* If you return a positive time interval (> 0) the read's timeout will be extended by the given amount.
* If you don't implement this method, or return a non-positive time interval (<= 0) the read will timeout as usual.
*
* The elapsed parameter is the sum of the original timeout, plus any additions previously added via this method.
* The length parameter is the number of bytes that have been read so far for the read operation.
*
* Note that this method may be called multiple times for a single read if you return positive numbers.
**/
- (NSTimeInterval)socket:(GCDAsyncSocket *)sock shouldTimeoutReadWithTag:(long)tag
                 elapsed:(NSTimeInterval)elapsed
               bytesDone:(NSUInteger)length;

/**
* Called if a write operation has reached its timeout without completing.
* This method allows you to optionally extend the timeout.
* If you return a positive time interval (> 0) the write's timeout will be extended by the given amount.
* If you don't implement this method, or return a non-positive time interval (<= 0) the write will timeout as usual.
*
* The elapsed parameter is the sum of the original timeout, plus any additions previously added via this method.
* The length parameter is the number of bytes that have been written so far for the write operation.
*
* Note that this method may be called multiple times for a single write if you return positive numbers.
**/
- (NSTimeInterval)socket:(GCDAsyncSocket *)sock shouldTimeoutWriteWithTag:(long)tag
                 elapsed:(NSTimeInterval)elapsed
               bytesDone:(NSUInteger)length;

/**
* Conditionally called if the read stream closes, but the write stream may still be writeable.
*
* This delegate method is only called if autoDisconnectOnClosedReadStream has been set to NO.
* See the discussion on the autoDisconnectOnClosedReadStream method for more information.
**/
- (void)socketDidCloseReadStream:(GCDAsyncSocket *)sock;

/**
* Called when a socket disconnects with or without error.
*
* If you call the disconnect method, and the socket wasn't already disconnected,
* then an invocation of this delegate method will be enqueued on the delegateQueue
* before the disconnect method returns.
*
* Note: If the GCDAsyncSocket instance is deallocated while it is still connected,
* and the delegate is not also deallocated, then this method will be invoked,
* but the sock parameter will be nil. (It must necessarily be nil since it is no longer available.)
* This is a generally rare, but is possible if one writes code like this:
*
* asyncSocket = nil; // I'm implicitly disconnecting the socket
*
* In this case it may preferrable to nil the delegate beforehand, like this:
*
* asyncSocket.delegate = nil; // Don't invoke my delegate method
* asyncSocket = nil; // I'm implicitly disconnecting the socket
*
* Of course, this depends on how your state machine is configured.
**/
- (void)socketDidDisconnect:(GCDAsyncSocket *)sock withError:(NSError *)err;

/**
* Called after the socket has successfully completed SSL/TLS negotiation.
* This method is not called unless you use the provided startTLS method.
*
* If a SSL/TLS negotiation fails (invalid certificate, etc) then the socket will immediately close,
* and the socketDidDisconnect:withError: delegate method will be called with the specific SSL error code.
**/
- (void)socketDidSecure:(GCDAsyncSocket *)sock;

/**
* Allows a socket delegate to hook into the TLS handshake and manually validate the peer it's connecting to.
*
* This is only called if startTLS is invoked with options that include:
* - GCDAsyncSocketManuallyEvaluateTrust == YES
*
* Typically the delegate will use SecTrustEvaluate (and related functions) to properly validate the peer.
*
* Note from Apple's documentation:
*   Because [SecTrustEvaluate] might look on the network for certificates in the certificate chain,
*   [it] might block while attempting network access. You should never call it from your main thread;
*   call it only from within a function running on a dispatch queue or on a separate thread.
*
* Thus this method uses a completionHandler block rather than a normal return value.
* The completionHandler block is thread-safe, and may be invoked from a background queue/thread.
* It is safe to invoke the completionHandler block even if the socket has been closed.
**/
- (void)socket:(GCDAsyncSocket *)sock didReceiveTrust:(SecTrustRef)trust
        completionHandler:(void (^)(BOOL shouldTrustPeer))completionHandler;

@end